The present invention relates to a display device, especially, to a liquid crystal display device.
Among various types of liquid crystal display devices, there is a liquid crystal display device in which a pair of substrates face each other in an opposed manner with liquid crystal material sandwiched therebetween. On respective pixel regions at a liquid-crystal-side of one substrate, pixel electrodes made of transparent conductive layers are formed; and, on a liquid crystal side of the other substrate, a counter electrode, which is made of a transparent conductive layer and corresponds in common to the respective pixel regions, is formed. The optical transmissivity of the liquid crystal material is controlled by electric fields generated between the respective electrodes in each pixel region, wherein molecules of the liquid crystal material are vertically aligned with respect to the substrates when no electric field is applied to the liquid crystal material (see Japanese Unexamined Patent Publication 2002-14353, Japanese Unexamined Patent Publication 1999-72793, Japanese Unexamined Patent Publication 2002-284290, for example).
In the liquid crystal display device having such a constitution, in order to obtain broad viewing angle characteristics, the pixel electrode is divided into a plurality of regions, thus forming divided electrodes (hereinafter referred to as “sub pixels”); and, on a liquid-crystal-side surface of a substrate at a side on which the counter electrodes are formed, projecting portions are formed at positions which face the centers of respective sub pixels (see Japanese Unexamined Patent Publication 2002-47217, for example). When an electric field is generated between the pixel electrode and the counter electrode, respective molecules of the liquid crystal material on the sub pixel exhibit a behavior in which the molecules tilt radially around the projecting portion as the center. Due to such a behavior, light which passes through the liquid crystal material can be irradiated to a viewer side in a broad range.
However, with respect to a liquid crystal display device having such a constitution, it has been confirmed that, when an electric field is generated between the pixel electrode and the counter electrode, a cruciform blackish pattern (hereinafter referred to as an “extinction pattern”) appears, as shown in FIG. 12, for every sub pixel of the pixel electrode, and, hence, a white display is not produced over the whole display surface.
The inventors of the present invention have pursued an investigation to determine the cause of the phenomenon and have eventually found that one one-stroke shaped blackish pattern of the extinction pattern agrees with the direction of the polarization axis of one polarizer of the polarizers which are formed on the respective substrates, while another one-stroke shaped blackish pattern thereof agrees with the direction of the polarization axis of the other polarizer.
It has been confirmed that this phenomenon is caused by the fact that, when the liquid crystal molecules are tilted in parallel with respect to the substrate, the liquid crystal molecules are collectively tilted along the directions of the polarization axes of the respective polarizers.
The present invention has been made on the basis of such circumstances, and it is an object of the present invention to provide a liquid crystal display device which can obviate the generation of the above-mentioned extinction pattern.